1. Field of the Invention
This invention relates to a process for the manufacture of reinforced plasterboard from gypsum (hemihydrate) and optionally reinforcing materials, preferably cellulose particles, with the addition of polyisocyanates in the production of plasterboard and/or the application of polyisocyanates to the surface of plasterboard.
The invention further relates to polyurea-modified, reinforced plasterboard with improved strength, water-resistance and flexural strength from gypsum (hemihydrate), optionally reinforcing materials, preferably cellulose particles, and polyisocyanates.
2. Description of the Prior Art
Plasterboard is presently widely used in the building industry, especially for so-called dry internal rendering, by virtue of its advantageous properties. It is customary to use plasterboard in which the tendency to fracture due to its brittleness has been reduced by facing it with cardboard or homogeneously incorporating cellulose particles. The wood-plasterboard described in DE-B No. 2,919,311 and homogeneously reinforced with wood chips (so-called wood plasterboard) constitutes a new variety of plasterboard.
Although plasterboards of this type have in some cases proven satisfactory, difficulties arise when they are used in so-called moist interiors, e.g. in cellars, kitchens and bathrooms. The difficulties are due to the tendency of plasterboard to swell in the presence of water and subsequently disintegrate.
It has been recommended to impregnate plasterboard with paraffin with a view to overcoming these difficulties. This method, however, provides only a limited water-repellency since the paraffins are only bound by adsorption.
It has now been found that plasterboard, especially plasterboard which has been strengthened with reinforcing materials of an inorganic nature such as glass fibers or with organic, natural, semi-synthetic or synthetic fibers, in particular plasterboard reinforced with cellulose particles, can be obtained with improved water-resistance combined with increased flexural strength if polyisocyanates are added during the process of producing the plasterboard and/or are applied to the surface of the finished plasterboard.